1. If a verb finishes with a vowel ( a,e,i,o,u,w,y),
get rid of the vowel and add on es i or ais i!
Cysgu Cysges i
Do you see?

2. Y ferf
Y gorffennol
Saesneg
cysgu
Cysgais i or cysges i
I slept
Deffro
Codi
Ymolchi
Gwisgo
Bwyta
Gwylio
Teimlo
Teithio
Siopa
Prynu
Gwario
chwarae

3. If a verb finishes with a consonant then just add on es i or ais i!
Siarad Siarades i
Do you see?

4. But
A very big But!
If a verb finishes with ed or eg get rid of both letters and add on es i or ais i.
cerdded cerddes I
Do you see?

5. Y ferf
Y gorffennol
Saesneg
eistedd
eisteddais
I sat
Edrych
Dewis
Symud
Siarad
Yfed
Rhedeg
clywed